1. Field of the Invention
This invention relates to a linear motor for developing a thrust force in the linear direction.
2. Description of the Related Art
In video cameras, electric rotating motors have been customarily used in association with automatic focusing systems or power zooming systems. The rotating motors are connected so that the rotational driving force developed by the motor will be transmitted through a speed reducing gear to a focusing ring or a zooming ring. However, the use of rotating motors in video cameras presents problems such as acoustic noises, vibrations, undesirable response characteristics and poor operating reliability, particularly with respect to the brushes or gearing.
In order to solve these problems, it has been tried in the prior art to drive the lens directly, that is, without the medium of brushes or speed reducing gears. However, a linear motor for this application has as yet not been realized because of the increased load when the lens is driven directly, so that problems are presented in the weight and size of the linear motor, as well as in power consumption and manufacturing costs.